By Elly Hilton, Madeleine Tsao, and Lacey Williams
One study the Dolphin Research Center conducted investigated the dolphins’ capacity to understand object permanence. The idea of object permanence is an animal’s ability to understand that an object still exists or is still there, even when it is hidden from view. Human babies also have to learn object permanence and do so at about one year old, hence the novelty of peek-a-boo for infants. DRC wanted to investigate if dolphins could also grasp this general concept using visual stimuli.
Three identical, opaque, black trash bins were placed in a row at the edge of the dock and weighed down with cement inside. The dolphin is called to attention by the trainer in front of the bins. A second trainer is standing on the opposite end of the dock with their back turned so they do not know the location of the stuffed animal in order to avoid cuing the dolphin. The first trainer puts the alligator into one of the three bins and places the lids on all three at the same time as the lids are connected by PVC piping to form a singular apparatus. The first trainer then turns around, taps the second trainer on the shoulder, and stands with their back to the bins. The second trainer goes up to the bins and gives the signal asking for the location of the hidden object. The dolphin will touch the bin it deems is the correct answer. The trainer then opens the bins and reveals the location of the stuffed animal to the dolphin, rewarding and reinforcing the dolphin’s choice when it chooses correctly.
We all had the opportunity to try out this experiment for ourselves during a training session with Talon. It had been a while since Talon had performed this behavior, and so we first familiarized Talon with the stuffed alligator toy. To do so we placed the alligator around the dock exposed so that Talon could remember to touch the alligator to complete the behavior and receive a reward. We also performed a few trials where the alligator was placed in one of the bins as in a full experimental trial, but the stuffed alligator’s tail was exposed so that Talon could still see. After familiarization, we performed several full trials where the alligator was completely hidden. These steps from fully exposed to fully hidden reflected the training steps undertaken during preparations for the formal experiment.
In the published paper, found here by Jaakkola et al. (2009), Talon was able to locate the stuffed alligator at a success rate greater than 80%, indicating statistical significance and showing that dolphins are capable of understanding the basic concept of object permanence.
A further step in the aforementioned study examined whether Talon could correctly locate the stuffed alligator after the bins had been swapped. This is the equivalent of what we know as the shell game where an object is hidden under one of three containers and then they’re all shuffled around before the individual has to figure out where the object is hidden. Even though the bin was moved over only one spot in front of Talon, he was not able to correctly choose the new location of the stuffed alligator. Instead, he would consistently choose the bin in the position where the alligator had originally been hidden.
Here is a video of Lacey performing a standard trial with Talon.
Here is a video of Elly performing a training trial with Talon, where the alligator was partially hidden.